Recovery of tin



Patented pa. 6, 1932 HARRY P. BASSE 'I'T, OF CYNTHIANA, Y

anoovnax or rm 1! o l lrawing.

This invention relates to the recovery of tin in substantially pure form from tin-.con-

taining material suchas scrufl, dross and the like which contains iron as an impurity.

Numerous processes have been devised for recovering t1n from material of the character recited above and various of such processes are commercially employed in the industries with varying degrees of success; 'For example, in the galvanizing industry, the recovery of tin is an. important'factor and numerous attempts have been made to recover the tin which otherwise would be wasted.

However, until the present no processes have been devised which will both recover the tin in substantially pure condition and without substantial loss. The processes now in use are particularly disadvantageous in that only a partial recovery of tin is efiected and the tin recovered is not pure but contains iron as an extremely disadvantageous impurity. The present process is designed to overcome these disadvantages and to provide means whereby tin may be recovered from tin-containing material in substantially pure form and without substantial loss. While the invention is particularly adapted for the recovery of tin in the galvanizing-industry it is not limited to use in this field but, as will be apparent, has a wide range of application.

In its broad aspects my process comprises heating tin-containing material such as scrufl', dross and the like to a temperature at least as high as the melting point of tin in contact with a high flash point petroleum oil, an organic reducing agent and an iron sulfiding agent, permitting the molten'tin to separate from the remaining mass and recovering the tin 'for use as desired. The treatment is preferably conducted in an ex,- ternally heated pot or other suitable containerand I have found that it is advisable, when an-open flame is employed: for heating, to

prevent the flame from coming into contact with the mass under treatment. The exact temperature of treatment is not important.v

The heat should be suflicient toraise the ma- .terial to at least the melting point of tin and should not great enough to cause the petroleum oil to ignite. In practice I have Application filed September 8, 1930. Serial No. 479,587.

.found that a temperature of approxiinately 240 C. is an advantageous temperature for operation. The exact time of treatment is also of no par'ticular importance. The time should be suflicient to assure thecomplete reduction of the tin and to permit the molten tin to settle to the bottom of the container.

Ordinarily, fifteen minutes is sufficient to complete the treatment.

As stated above, a high flash point petroleum oil is employed in the treating composition. By a high flash petroleum oil as employed-herein is meant a petroleum oil which does not ignite at orslightly above the melting point of tin. The oil commercially known as 600W is a specific example of the type of oil which I employ. The purpose of this oil is to serve as a vehicle for the organic reducing agentemployed in theprocess and to absorb oil soluble impurities from'the mass under treatment. i

The primary purpose of employing an organic reducin agent is to readily reduce. the

tin' oxide (Sn) in the material under treat ment to tin. Numerous organic reducing agents may be employed in the practice of the process. The primary requisite of the reducing material is that it shall be capable of quickly converting the tin oxide present into tin at or slightly above the melting point of tin. A fatty oil or fat having reducing properties, such as peanut oil, cotton seed oil, or the like might advantageously be used. In the preferred practice ofthe process peanut oil is employed. Unsaturated fatty acids such as oleicacid or the like may also be.

employed. Resins having reducing properties under the conditions of operation of the process may also be employedwith success. I have-used commercial rosin advantageous- 1y, In addition to the foregoing, other organic compositions having similar reducing I stood that the .term organic reducing agent as employedin the claims is intended to inproperties may be employed and it is underv the character set forth and is ordinarily difficult of removal. I have found however I that the iron present in the material may be readily removed b sulfiding the iron dur ing the process. hen this is done the iron sulfide is carried by the petroleum oil while themolten tin settles to the bottom' of the container employed, the iron being separated from thetin in this manner. As a sulfiding agent I prefer to employ a mixture of lime of the amount required to completely convert the sulfurto sulfide. A resulting mixture in the form .of 2GaO .CaS is the preferred proportion, Calcium sulfide may also be employed as a sulfiding agent orthis material together with a small'amount of free sulfur may be employed.

' The proportions of ingredients obviously must be varied according to the nature of the material under treatment- For example, the amount of reducing agent employed will depend upon the percentage 'of tin oxide in the material. The amount of sulfiding agent will depend upon the amount of iron present. The amount of petroleum oil employed will, as

will be apparent, depend upon the amount of reducing "agent employed and the percentage of oil soluble impurities present and the amount of iron sulfide formed.

For the sake of a specific example the following may be considered as-illustrative of the invention. According to this example 78 grams of scruff were treated with 2 grams of calcium sulfide, 0.5 grams of sulfur, 20 grams of 600W oil and 4 vgrams of commercial rosin at a temperature of approximately 240 C. for 15 minutes. The molten tin which separated and collectedat the bottom of the container was drawn off by a tap.

' As will be obvious from the foregoing, the

petroleum oil will after use in the process contain numerous impurities but the oil may be re-used'in the process by filtering out these impurities. Since there, is no substantial loss ofoil it will be obvious that the oil may be used for long periods of time without replacement. p w While I have described in detailthe preferred practice of my process and the preferred composition to be employed in connection therewith, it is to be understood that the t details of procedure may be variously modias an impurity which comprises heating the.

material to be treated at approximately the melting point of tin in contact with a high flash point petroleum oil, an organic reducing agent, and calcium sulfide, separating the a()) and sulfur, the lime being in excess molten tin from the mass, and recovering the tin.

2. The herein describedprocess of recover- I ing tin from tin-containing material such as scrufl', dross and the 11ke wh ch contains iron from the mass, and recovering the tin.

- 3. The herein described process of recover:

ing tin from tin-containing material such as scrufi, dross and the like which contains iron as an impurity which comprises heating the material to be treated at approximately the melting point of tin in contact with a high flash point petroleum oil, peanut'oil, and an ironsulfiding agent comprising calcium sulfide, separating the molten tin from the mass,

and recovering the'tin.

4. (The herein described process ofrecovering tin from tin-containing material such as V scruff, dross and the like which'contains iron as an impurity whichv comPrisesheating the material to be treated at approximately the melting point of tin in contact with high flash point petroleum oil, an unsaturated fatty acid, and an iron sulfiding agent comprising calcium sulfide, separating the molten tin from the mass and recovering the tin.

5. The herein described process of recovering tin from tin-containing material such as scruflt', dross and the like which contains iron too as an impurity which comprises heating the material to be treated at approximately the melting point of tin in contact with a high flash point petroleum oil, oleic. acid, and an iron sulfiding agent comprising calcium Sl1l fide, separating the molten tin from the mass, and recovering the tin.

6. The herein described process of recove'ring tin from tin-containing material such as scruff, dross and the like which contams iron as an impurity which comprises heating the material to be treated at approximately the melting point of tin-in contact with a high flash point petroleum oil, a resin capable of reducing tin oxide to tin at the melting point of tin,and an iron sulfiding agent comprising calcium sulfide, separating the molten tin from the mass, and recovering the tin.

7. The herein described process of recovering tin from tin-containing material such as scrufi', dross and the like which contains iron as an impurity which comprises heating the material to be treated at approximately the melting point of tin in contact with a high flash point petroleum oil, commercial rosin and an iron sulfiding agent comprising calcium sulfide, separating the molten tin from the mass, and recoverin the tin.

8. The herein descri ed process of recovering tin from tin-containing material 'such as scrufi, dross and the like which contains iron as as impurity which comprises heating the material to be treated at approximately the melting point of tin in contact with a hi h flash point petroleum oil, an organic re ucin agent, and a mixture of lime and sulfur, t e lime bein in excess of the amount required to convert t e sulfur to sulfide, separating the molten tin from'the mass, and re- 10 covering the tin.

9. A com osition of the character described whic comprises a high flash point petroleum oil, an organic reducing agent, and an iron sulfiding agent comprising calcium sulfide.

10. A composition of the character described which comprises a high flash point petroleum oil, a fatty acid glyceride, and an iron sulfiding agent comprising calcium sul- 2 fide.

11. A composition of the character described which comprises a high flash point petroleum oil, peanut oil, and an iron sulfidmg agent comprising calcium sulfide.

12. A composition of the character described which comprises a high flash point petroleum oil, an unsaturated fatty acid, and an iron sulfiding agent comprising calcium" sulfide.

13. A composition of the character described which comprises a high flash point petroleum oil, oleic acid and an iron sulfidmg agent comprising calcium sulfide.

14.-A composition of the character described which comprises a high flash oint petroleum oil, rosin, and an iron sul ding agent comprising calcium sulfide.

15. A composition of the character de scribed which comprises a high flash point 40' petroleum oil, an organic reducing agent,

and a mixture of lime and sulfur, the lime being in excess of the amount required to effe lzit 1 (like complete conversion of the sulfur to so e.

In testimony whereof I aflix m signature.

HARRY P. B SSETT. 

